Frame Forwarding Apparatus for Converting Vlan Identifiers

1. A frame forwarding apparatus equipped with a plurality of line interfaces, connected to an IP packet forwarding apparatus through one of said line interfaces and connected to subscriber terminals through the other line interfaces, said frame forwarding apparatus comprising: a line information table comprising a plurality of entries, each defining a line number of a physical line connected to one of said line interfaces and flag information for indicating whether the physical line is connected to said IP packet forwarding apparatus or to one of said subscriber terminals; a VLAN bundling table comprising a plurality of entries, each defining the correspondence of subscriber side line information with IP packet forwarding apparatus side line information and subscriber terminal's MAC address; and a frame forwarding processing unit for controlling forwarding of frames each including a VLAN identifier, between each of said subscriber terminals and said IP packet forwarding apparatus, wherein each entry of said VLAN bundling table includes a physical line number and a subscriber VLAN identifier defined on the physical line having the physical line number as said subscriber side line information and a physical line number of the physical line connected to said IP packet forwarding apparatus and a group VLAN identifier defined on the physical line as said IP packet forwarding apparatus side line information, and at least one group of the entries in said VLAN bundling table includes the same group VLAN identifier as each other as said IP packet forwarding apparatus side line information, wherein when a frame is received through one of said line interfaces, said frame forwarding processing unit (1) judges whether the frame is received from one of said subscriber terminals or from said IP packet forwarding apparatus by referring to the flag information in said line information table based on the line number of the physical line connected to the one line interface; (2) converts, by referring to said VLAN bundling table, the subscriber VLAN identifier given in the frame into the group VLAN identifier defined in one of said entries when the frame is judged as one having been received from one of said subscriber terminals, and forwards the frame to said IP packet forwarding apparatus; and (3) converts a group VLAN identifier given in the frame into the subscriber VLAN identifier defined in one of said entries when the frame is judged as one having been received from said IP packet forwarding apparatus and addressing one of said subscriber terminals with a destination MAC address, and forwards the frame to one of said physical lines corresponding to the destination subscriber terminal through one of said line interfaces.

2. The frame forwarding apparatus according to claim 1 , wherein said frame forwarding processing unit: conducts a first search of said VLAN bundling table, when forwarding the frame received from one of said subscriber terminals, for an entry including the subscriber VLAN identifier given in the received frame as the subscriber side line information and converts the subscriber VLAN identifier of the received frame into the group VLAN identifier specified in an entry, search by the first search; and conducts a second search of said VLAN bundling table, when forwarding the frame received from said IP packet forwarding apparatus, for an entry having a MAC address matched with the destination MAC address of the received frame and converts the group VLAN identifier of the received frame into the subscriber VLAN identifier specified in an entry searched by the second search.

3. The frame forwarding apparatus according to claim 2 , wherein said frame forwarding processing unit outputs the frame received from one of said subscriber terminals to one of said line interfaces corresponding to the physical line number specified by the IP packet forwarding apparatus side line information in the entry searched by the first search, and outputs the frame received from said IP packet forwarding apparatus to one of said line interfaces corresponding to physical line number specified by the subscriber side line information in the entry searched by the second search.

4. The frame forwarding apparatus according to claim 1 , wherein all of said one group of entries having the same group VLAN identifier include the same physical line number and the same subscriber VLAN identifier to each other as said subscriber side line information.

5. The frame forwarding apparatus according to claim 1 , wherein all of said one group of entries having the same group VLAN identifier include the same physical line number and different subscriber VLAN identifiers from each other as said subscriber side line information.

6. The frame forwarding apparatus according to claim 1 , wherein the entries of said VLAN bundling table form a plurality of groups, each comprising a plurality of entries including the same physical line number as each other as said subscriber side line information, and the plurality of entries belonging to the same group include the same group VLAN identifier as each other as said IP packet forwarding apparatus side line information.

7. The frame forwarding apparatus according to claim 6 , wherein at least one of said plurality of groups comprises a plurality of entries including the same physical line number and different subscriber VLAN identifiers as each other as said subscriber side line information and another group comprises a plurality of entries including the same physical line number and the same subscriber VLAN identifier as each other as said subscriber side line information.

8. The frame forwarding apparatus according to claim 1 , wherein said frame forwarding processing unit searches said VLAN bundling table when a frame including a broadcast address as said destination MAC address was received from said IP packet forwarding apparatus, for a plurality of entries each having the group VLAN identifier matched with the group VLAN identifier given in the received frame, converts the received frame into a plurality of frames each having the subscriber VLAN identifier specified in each of searched entries, and selectively outputs each of the frames to one of said line interfaces corresponding to the physical line number specified a searched entry.

9. The frame forwarding apparatus according to claim 1 , wherein a group of said other line interfaces connected to the subscriber terminals is provided with a function of terminating a Passive Optical Network (PON) frame and connected to a plurality of subscriber terminals via an optical fiber and branch fibers coupled to the optical fiber with an optical coupler.